1. Priority
Priority is claimed to European Patent Application No. 11 160 513.5, filed Mar. 30, 2011, the disclosure of which is incorporated herein by reference in its entirety.
2. Field of the Invention
The field of the present invention is conveying devices for free-flowing fine-particle solids, in particular for powdery and/or granular (mixed) material, especially plastic granulate, such as are used in a filling plant for polymer granulates.
3. Background
The gravelly product which accumulates in the reactor in the manufacture of thermoplastic plastics is plasticized in an extruder and shaped into single strands, which are cut into granulates by means of a blade which rotates in the granulating tool. In a further step, this product can be provided with further components by compounding.
By compounding is meant, in polymer processing, the manufacture of finished plastic moulding material, the compound, from the plastic raw materials, with the addition of fillers and reinforcing agents, softeners, adhesion-promoting agents, lubricants, stabilizers, etc. The compounding predominantly takes place in extruders and comprises the process operations conveyance, melting, dispersion, mixing, degassing and pressurization.
In granulation, the melt is then pressed through the openings in a die base, so that after this, in the case of strand granulation, melt strands are initially produced, which then in the granulation produce cylindrical granules, or else, in the case of head granulation, are cut directly at the outlet on the die base and then produce lenticular or spherical granules. Granulation can also take place, for instance, in a liquid flow, which cools the granules and largely prevents agglomeration. The granulate is subsequently dried and sifted.
Subsequent to the post-manufacture or post-compounding granulation, the product is generally conveyed pneumatically to a silo or bunker. After this, the bulk material is removed from the silo or bunker and filled into containers or silo vehicles, or the bulk material is bagged into big bags, octabins or sacks. In each of these steps, dusts/deposits can be formed, for example, by abrasion, which dusts/deposits, in addition to the bulk material itself, can then cause contamination when the bulk material is changed.
Typical bulk materials are, for example, construction materials, such as topsoil, sand, gravel, ballast, cement, other mineral products, such as ore, road salt, and foods, such as grain, sugar, table salt, coffee, flour, as well as powdery products such as pigments, fillers, granules, pellets, etc.
At the same time, the demand for flexibility is constantly increasing, so that in a filling plant equipment can be exchanged according to needs. For instance, in the case of a bulk material, there may be a demand for a sifter (dedusting unit) to remove fine particles, whilst for other bulk materials only a conveying pipe is necessary. Moreover, the investment costs are not inconsiderable, so that a flexible solution for the use of, for instance, a conveying pipe at various locations in a plant is enabled.
DE 195 272 40 C1 describes a conveying device, wherein a portion of the conveying line between two rigidly spaced counter bearings is arranged such that it is exchangeable and the exchangeable conveying line portion is configured to be telescopic under the action of a tension spring and the ends of the telescopic arrangement are supported against the counter bearings. The design-conditioned, appropriate cleaning effort for the avoidance of contamination as soon as another solid is conveyed, particularly in the pipe flange region and in the pipe inner contour, is disadvantageous.
The demand for easy washability of conveying devices prior to the conveyance of another bulk material type is made, however, with increasing frequency.